1. Field of the Invention
The present invention relates to an electronic printer, and more specifically, to a thermal printer and related method for printing pictures having a stampable surface.
2. Description of the Prior Art
Thermal printers are used in computer systems to print digital images. One type of printer uses a printhead to heat a dye ribbon to transfer dye of different colors to a print medium. A typical dye ribbon comprises dye regions or frames of colors that can be printed in proportions to approximate true color, and a transparent overcoating region that can be disposed over printed dye to protect the printed dye from moisture degradation. Currently, this type of thermal printer is commonly used to print digital photographs via direct connection to a personal computer or digital camera.
As mentioned, the overcoating used is a water or oil resistant overcoating that protects the printed ink from running, fading, and smudging due to contact with moisture, water, and oil from handling. The resistant overcoating is disposed onto a printed picture by heat output from the thermal printhead in much the same way as the colored dye.
In many applications, it is desirable to be able to apply a traditional ink stamp to a photograph. Whether for official documentation, copyrighting, or forgery protection, users may want to apply an ink stamp, such as a seal or official identification stamp, to a picture printed by a digital thermal printer. However, the physical properties of the water or oil resistant overcoating are such that it does not take an externally applied stamp well. On the contrary, the resistant properties act against allowing an ink stamp to be applied to the overcoating resulting in a semi-permanent stamp or a stamp that is easily smudged or even completely removable. One method of avoiding this result is to use a permeable overcoating to allow the stamp ink to transfer to the print medium having the disposed printing dye. However, this practice is found to be inadequate, as it does not prevent other sources of moisture from entering the print and degrading the image.
Please refer to FIG. 6 showing a cross-section of a thermally printed picture 60. The picture 60 includes a print medium (paper) 62 having thermally printed dye layers 64y, 64m, and 64c respectively for yellow, magenta, and cyan dye protected by a permeable overcoating layer 68. The dye layers 64y, 64m, and 64c and overcoating layer 68 are printed to the paper 62 by a thermal printer. When a water based ink stamp is applied externally to the picture 60, water 72 from the ink penetrates the permeable overcoating 68 and acts to dissolve dye of the layers 64y, 64m, and 64c degrading the image. Consequently, this approach does not fully protect the printed image from damage.
It is therefore a primary objective of the claimed invention to provide a thermal printer capable of printing resistant and stampable overcoating and a related method for printing an image to solve the abovementioned problem.
Briefly summarized, the claimed invention includes a printer body, a thermal printhead installed in the printer body, a print ribbon installed in the printer body, and a control circuit for controlling the thermal printhead and the print ribbon. The print ribbon has regions of colored dye, regions of ink stamp vehicle resistant overcoating, and regions of stampable overcoating capable of accepting an ink stamp. A sensor is provided to detect the print ribbon and output a ribbon signal. The control circuit is capable of receiving the ribbon signal and controlling the thermal printhead and the print ribbon according to received image signals to print pictures having stampable images.
According the claimed invention, the print ribbon can be provided as two print ribbons, one print ribbon having regions of colored dye and regions of resistant overcoating, the other print ribbon having regions of stampable overcoating capable of accepting an ink stamp, both print ribbons being interchangeably installable in the printer body. And, the sensor is capable of detecting and distinguishing between the two print ribbons and outputting a corresponding ribbon signal.
According to the claimed invention, a method for printing an image with a thermal printer includes printing an image to a print medium by disposing colored dye onto the print medium, printing resistant overcoating over the image printed on the print medium, and printing stampable overcoating over the resistant overcoating.
It is an advantage of the claimed invention that stampable overcoating is applied over the resistant overcoating by the thermal printer so that ink stamps can be applied to the stampable overcoating while being prevented from damaging the image by the resistant overcoating.
It is a further advantage of the claimed invention that an ink stamp applied to a picture printed with the claimed invention is not easily smeared and does not degrade the image on the picture.
It is a further advantage of the claimed invention that the sensor can detect an installed print ribbon and set parameters thermal printhead parameters automatically.
These and other objectives of the claimed invention will no doubt become obvious to those of ordinary skill in the art after reading the following detailed description of the preferred embodiment that is illustrated in the various figures and drawings.